The main objective of this proposal is to establish the role of Shope fibroma virus (SFV) in the genesis of abnormal growth. For this purpose two strains of SFV that behave entirely different in cell cultures, one promoting the formation of "foci" and the other inducing rapid cell lysis, will be investigated. Comparative studies include determination of host DNA synthesis, characterization of virus-induced and structural proteins and analysis of the viral DNA by restriction endonucleases. The properties of the cells in the "foci" will be examined to determine whether they have been permanently modified. In addition, transformation of primary cell cultures with SFV will be attempted. For these studies the viral genome will be inactivated and/or the cells will be pretreated with tumor promoters and chemical carcinogens. Information sought from the proposed work can be of potential importance to explain the molecular basis of both viral and chemical carcinogenesis.